I'm currently using this setting for my 13th Age campaign, and it's been a great fit for my group. It has a good balance between defining enough, so that I know, in a general way, what each portion of the world is "all about," but doesn't define so much that I can't insert my own details. It has a great take on the pantheon, which is unique to Midgard. Personally, I like some of the more unusual races that play a larger role in Midgard: kobolds, ravenfolk, gearforged, and minotaurs. The world is large enough that it features areas that are influenced by the culture and myths of Scandinavia, Eastern Europe, Arabia, the Italian Renaissance, and even a bit of post-apocalyptic goodness. The world is sufficiently dark, where you know heroes are needed, but not so dark that it's overly Gothic or gritty.

The source books for Midgard are also great additions to my game, and are worth mentioning. There are supplements for several major areas as well as some of the races I mentioned above. And the adventures that I've played through have all been a blast.